The invention relates to detection of a failure of a wheel speed sensor on a locomotive propelled by AC traction motors. Specifically, the invention is a method for determining the status of a group of speed sensors and establishing a hierarchy of resultant actions. Locomotives used for hauling applications are generally equipped with speed sensors coupled to respective traction motors or to the axles driven by the motors. The speed sensor data or information may be used to control various functions like torque production, adhesion optimization, as well as speed control and indication. The speed sensor data may also be utilized to detect a locked axle condition. Typically, in such locomotives, multiple inverters are connected to the same DC bus and such inverters may be used to drive one or more traction motors. When any one of the speed sensors fails it is possible to have the symptoms of the failure be detected by controllers of other axles causing them to shut down before the true symptom is detected. For example, if one of the speed sensors reads a low value of speed, the reference speed calculator will follow the erroneous low value input on the assumption that it is the true speed. Such a false reference following will cause all the axles to reduce torque as it would appear, though incorrectly, that the axles are slipping. This may result in the affected axle regenerating and driving power back into the DC bus. Similarly, all of the axles may be regenerating and thereby causing the DC bus voltage to be driven higher. This regeneration could cause a high voltage shut down condition. In addition, any motor controller could shut down because of an over-current especially in light of the devices typically having lower current rating as the voltage increases. The result of the above events would be to cause an improper inverter to shut down and an erroneous malfunction indication to a maintainer.
Over-voltages, over-currents, and erroneous failure indications result in costly efforts for maintainers. Thus, there is a need for a low-cost method to reliably determine when a speed sensor has failed.
A system and method for detecting the failure of a speed sensor on a locomotive propelled by an AC traction motor. The system includes a locomotive including a processor for executing a detection method. The method comprises conducting an evaluation of symptoms exhibited by a speed sensor. A health value representative of health of the speed sensor is modified as a function of the evaluation and a modified health value is generated as a result from the modification of the health value. A motor control methodology is selected which is responsive to the modified health value.
A storage medium encoded with a machine-readable computer program code for detecting a failure of a speed sensor on a locomotive propelled by an AC traction motor, the storage medium including instruction for causing a controller to implement the disclosed method.
A computer data signal for detecting a failure of a speed sensor on a locomotive propelled by an AC traction motor, the computer data signal comprising code configured to cause a processor to implement the disclosed method.